Blasting machine



J. STUART, 2D

BLASTINLE March 9, 1943.

MACHLNE Filed Jan. 10, 1940 JQSEPH STUAR T 31 has not been as desirablemachine is at its .highest value.

. Patented Mar. 9, 1943 BLASTING MACHINE Joseph smart, 11, Wilmington,Del., assignor. to Hercules Powder Company, Wilmington, Del.,acorporation of Delaware Application January 10, 1940, Serial No.313,264

7 Claims.

This invention relates to an improved portable dynamo for supplying thenecessary electrical energy for-firing a plurality of electric firingdevices and more particularly to an improved blasting machine for firingelectric blasting caps.

The blasting machines having a capacity in excess of ten caps areusually those of the push down type, that is, the dynamo is operated bya rack bar that turns a pinion gear on the armature shaft. Machines ofthis type are in general use for firing a plurality of caps and arefurnished in such sizes that an operator may fire upto 30, 50 or 100caps at one time. The industry has also been supplied with blasting machines operated by a hand crank and a series of gears, but, due todiificulti'es in obtaining maxi mum current output quickly, thistypemachine as the "push down type.

While the push down type machine is the most satisfactoryblastingmachine known to the art there are difiiculties-encountered inits operation. This type of machine is unsatisfactory in its operationbecause the amount of. current developed depends upon the force or speedwith whichthe rack bar is operated. The current.

loss of labor and decrease in production.

The electrical energy generated by means of a push down blasting machineis usually delivered to the firing line upon the closing of a meat thattime when the energy generated by the This theory and operation alwayholdstrue but since the electrical energy is dependent upon the speedwith which the armature rotates and the speed of rotation depends uponthe operator, there may be delivered to the firing line electricalenergy of widely different values. The energy developed by the handcrankmachine will vary as much as the push down type due to difierent speedsof operation.

The firing or detonation of a modern electric blasting cap usuallyoccurs within 0.01 second after the energy is applied to it, so that itis apparent that the effectiveness of the blasting depends on itsoperation immediately upon closure of the mechanical switch.Unfortunately,-the

- switch points are liable to become corroded or pitted and in someinstances, it is observed that the switch does not close with positiveaction, but completes and opens the circuit many times before finally'closing, with the result that the effective energy delivered by themachine during the critical interval, is much reduced.

Numerous attempts have been made to overcome the deficiencies of theoperators, and the effects of wear. Larger machines have beenconstructed, but the advantages are ofiset by increased welghtand cost.One of the most promising developments ha been the employment ofrelatively light and inexpensive electrical condensers, placed acrossthe terminals of the generator.

However, in practice, the benefits of the condenser are partly nullifiedby the fact that the discharge of the condenser produces heavy arc"- ingat the switch points and shortens their life. The discharge alsoconsumes power and the energy of the condenser, instead of aiding infiring the caps, is partly lost at the switch.

'It is the object of this invention to provide a dynamo whichcan deliyerelectrical energy to the firing line only when the voltage has reached apredetermined value.

chanical switch which is positioned to be operated It is a furtherobject of this" invention to provide a blasting machine for initiatingelectric firing devices which cannot deliver a current a a blastingmachine in which the current output does not vary with the operation.

A 'still further object of this invention is to provide a. blastingmachine having voltage con- -trol or regulator tube which prevents thedelivery of any but a definite minimum current. a I Other and furtherobjects of this invention will be obvious upon an understanding of theillustrative embodiments about to be described or will beindicated inthe appended claims and various advantages not referred to herein willoccur to one skilled in the art upon employment of the invention inpractice.

A preferred embodiment of the invention has been chosen for purposes ofillustration and de--,

scription and is shown in the accompanying drawing forming a part of thespecification wherein;

Fig. 1' is a front elevation view, partly in section, of a preferredembodiment of the invention illustrating a push down" type blastingmachine.

Fig. 2 is a side elevation view, partly in section, of an alternativeembodiment; of this invention and consists of a hand crank blastingmachine.

Figs. 3, 4, and indicate the various electric circuits which may be usedin the embodiments shown in Figs. 1 and 2; and

Fig. 6 shows an alternative method of using the principle of thisinvention by substituting for the generator a source of current such asa battery or other electrical energy supply.

Described generally the energy supplying machines of my inventioncomprises a source of electrical energy such as a generator, battery orelectrical power lines connected through a suitable circuit including avoltage control or regulator tube and contact terminals. To theterminals of th machine of my invention there will be connected 2.suitable number of electric firing devices and, upon proper operation ofthe generator or closing of switches, the electrical charge is fed intothe generator or dynamo circuit including the voltage control orregulator tube which, upon building up to a predetermined value, willdischarge into the firing line and cause the detonation or ignition ofthe firing devices.

Referring again to the drawing and more particularly to Figs. 1 and 2,there is shown a suitable casing I in which is mounted a voltage controlor regulator tube 2. Also within casing I there is mounted a source ofelectric current such as the generator or dynamo 4. The armature of thisgenerator 4 may be rotated by the rack bar 5 having handle 6 throughgears 1 (Fig. 1) or by hand crank 9 through gears 10 (Fig. 2). In eithercase the generator 4 produces electrical energy and establishes avoltage potential across the electrodes of the voltage control tube 2.At a given voltage the voltage control tube 2 discharges throughterminals or binding posts II to which may be attached any suitablenumber of firing devices.

Typical methods of electrically connecting the generators shown in Figs.1 and 2, are shown in Figs. 3, 4, and 5.

In Fig. 3 a shunt wound generator is shown with one of its outputterminals electrically connected directly to one of the binding posts orcontact terminals II and with its other output terminal connected to theother binding post ll through the voltage control tube 2.

.It is to be noted that the generator circuit including thevoltagecontrol tube 2 and the contact terminals H to which maybe connected aplurality of firing caps is permanentlyclosed through the outputterminals of the generator thereby forming a fixed electrical circuitthrough the terminals. I

In Fig. 4 a compound wound generator is shown which has its outputterminal connected to the binding posts H in the same manner asdescribed above.

In the wiring diagram of Fig. 5, there is shown a condenser l2 acrossthe terminals of the shimt wound generator, located between thegenerator and the tube, to cause the current to build up to the desiredpoint and to increase the capacity of the blasting machine.

In addition to the use of the manually operated generators, theelectrical energy needed for firing the firing devices may be suppliedby a battery I such as is shown in Fig. 6 or other well known sources ofelectrical energy such as any suitable power line available at theblasting location. Thus, a high voltage, low current battery 14 may beconnected through a switch I5 to the condenser l2 and voltage regulatortube 2. The battery may be of the type commonly known as a B battery,having a high internal resistance, which is designated by the resistanceii. If the battery were connected directly to the firing line by closingthe switch, misfires would probably result, because the internalresistance of the battery would limit the current to a low valueinsufiicient to fire the electric blasting caps. However, when thecondenser and regulator tube are used, upon closing the switch thecondenser is charged, until the critical voltage of the regulator tubeis reached. The regulator tube then automatically discharges the energystored in the condenser into the firing line. By suitable choice ofcircuit constants a heavy current may be passed through the firingcircuit, even though the battery which supplied the original energy iscapabl of providing only a fraction of this current.

A preferred voltage control tube 2 may be of the type manufactured byWestinghouse and known as type KX-642. While this tube hasthree'electrodes only two'are utilized and accordingly only twoelectrodes are illustrated on the drawing. The tube is rated as follows:

Breakdown voltage A. C.-R. M. S.

volts 300-500 Maximum discharge current for 2 sec.

Maximum short circuit current at which tube will clear at first currentzero:

At 230 volts amperes 10 At 115 volts do 15 Maximum overall length inches5 Maximum diameter do The tube may be arranged to allow the passage ofcurrent of any predetermined voltage and thus by using a tube of theproper rating in the blasting machine of this invention, any desirednumber of firing devices may be fired. The tubes preferably are ratedtobreak down when sumcient current is applied to insure the firing of 50electric blasting caps. It will be understood however that I maymanufacture a blasting machine by using a tube which will break downunder any specified breakdown voltage. Thus, I

have iound that I may, by using the proper tube, produce a blastingmachine having any desired cap rating. r

, From the foregoing description it will be seen that the presentinvention provides a blasting machine which cannot discharge into thefiring line unless sumclent current is available to fire all devicesconnected on the line. This eliminates all shots in which part or all ofthe caps fail to shoot due to lack of suificient current in the line.The use of the control tube insures proper operation of the machine andprevents the use of generators which are defective. It allowsinexperienced operators to be eificient blasters because they can setofi a series of blasting caps only when they operate the machineproperly. It allows a closer calibration of machine capacity, and givesassurance each shot fired will be successful. The machines withregulator tubes also have the advantage of not requiring a mechanicalswitch and thus pitting of switch with the attending loss of power is nolonger a factor. These advantages have not been obtainable with theblasting machines used heretofore and the machines of the presentinvention are, therefore, a definite improvement over the priormachines. The machine is rugged in construction and the tubeincorporated therein is located in a manner which provides assurancethat it will function perfectly even under the rough usage to whichblasting machines may be subjected.

As various changes may be made in the form, construction, andarrangement of'the parts herein without departing from the spirit andscope of the invention and without sacrificing any of its advantages, itis to be understood that alli matter herein is to be interpreted asillustrative and not in a limiting sense.

What I claim and desire to protect by Letters Patent is:

1. In a blasting machine the combination of a manually operable dynamo.contact terminals adapted to receive a plurality of blasting caps inelectrical contact therewith conductor elements forming a fixed circuitbetween said dynamo and said terminals whereby energy from said dynamomay be conducted instantaneously from said dynamo directly to saidterminals, and a voltage control tube in said circuit adapted to permitthe flow of said energy under a predetermined electrical potential.

2. In a blasting machine the combination of a manually operable dynamo,contact terminals adapted to receive a plurality of blasting caps inelectrical contact therewith, conductor elements forming a circuit infixed electrical contact with said dynamo and said terminals wherebyenergy from said dynamo may be conducted instantaneously from saiddynamo directly to said terminals, and a voltage control tube in saidcircuit adapted to permit the flow of said energy under a predeterminedelectrical potential.

3. In a blasting machine the combination of a manually operable dynamo,contact terminals adapted to receive a plurality of blasting caps inelectrical contact therewith, a circuit permanently connecting saiddynamo with said terminals whereby energy from said dynamo may beconducted instantaneously from said dynamo directly to said terminals,and a voltage control tube in said. circuit adapted to permit the flowof said 'energy under a predetermined electrical potential. 4. In ablasting machine the combination of a manually operable dynamo, contactterminals adapted to receive a plurality of blasting caps in electricalcontaot therewith, conductor elements forming a closed circuit throughsaid dynamo and said terminals including a plurality of blasting caps,whereby energy from said dynamo may be conducted instantaneously fromsaid dynamo directly to said terminals, and a voltage control tube insaid circuit adapted to permit the flow of said energy under apredetermined electrical potential.

5. In a blasting machine the combination of a manually operable dynamoincluding a dynamo circuit,- contact terminals in said circuitadapted toreceive a plurality of blasting caps in electrical contact therewith,and a voltage control tube in said dynamo circuit adapted to permit theflow of energy from said dynamo directly and instantaneously to saidterminals at a predetermined electrical potential.

6. In the method of firing a plurality of electrical firing devices witha source of electrical energy which includes a manually operable dynamo,the step of directly subjecting an electrode of a voltage control tubeto an electrical potential flowing directly from said dynamo to saidelectrode, and the step of permitting the instantaneous flow of saidenergy to said firing devices under a definite'predetermined voltagepotential.

7. In a blasting machine, the combination of a manually operable dynamoincluding a dynamo circuit, contact terminals in said circuit adapted toreceive a plurality of blasting caps in electrical contact therewith,and a switchin said cir cuit, said switch consisting of a gas-filled,cold cathode tube having a break-down voltage between about 300 andabout 500 volts, and a current capacity of about 50 amperes for at least2 seconds, said switch being adapted to automatically permit the flow ofenergy from said dynamo to said terminals at a predetermined electricpotential.

. JOSEPH STUART, II.

